Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings
Authors: Roger Chou, Tracy Dana, Rebecca Jungbauer
Journal: Annals of Internal Medicine (2022)

LettersSeptember 2022Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community SettingsFREECorrection(s) for this article:CorrectionsNov 2022Correction: Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community SettingsFREERoger Chou, MD, Tracy Dana, MLS, Rebecca Jungbauer, DrPHRoger Chou, MDPacific Northwest Evidence-based Practice Center, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, Oregon, Tracy Dana, MLSPacific Northwest Evidence-based Practice Center, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, Oregon, Rebecca Jungbauer, DrPHPacific Northwest Evidence-based Practice Center, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, OregonAuthor, Article, and Disclosure Informationhttps://doi.org/10.7326/L22-0272 SectionsSupplemental MaterialAboutVisual AbstractPDF ToolsAdd to favoritesDownload CitationsTrack CitationsPermissions ShareFacebookTwitterLinkedInRedditEmail This is the eighth update alert for a living rapid review (1) on the use of masks for the prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. The first 3 updates (2–4) were monthly, after which the interval was switched to bimonthly (5, 6). Beginning in June 2021, the interval was extended to biannually. For this update, searches were done from 3 December 2021 to 2 June 2022 using the same search methods as the original review. Inclusion was restricted to randomized trials and observational studies that controlled for confounders. Non–peer-reviewed studies were excluded unless they were based on data collected after February 2021 to capture evidence on mask use in the B.1.617.2 (Delta) and B.1.1.529 (Omicron) variant predominant periods. The update searches identified 1592 citations. No new randomized controlled trials (RCTs) and 5 new observational studies on the association of mask use and SARS-CoV-2 infection met inclusion criteria (Supplement Table 1). Three studies were done in community settings (7–9), and 2 studies (10, 11) were done in health care settings. One preprint study (9) of mask use in community settings collected data during Delta and Omicron predominant periods; the other studies were done before the emergence of these variants. All studies had methodological limitations, including unclear or low participation rate, potential recall bias, and failure to report attrition or missing data (Supplement Table 2).Community SettingsThree new observational studies (7–9), all done in the United States, evaluated the association between mask use in community settings and risk for SARS-CoV-2 infection.In previous updates, the evidence for mask use versus no use for prevention of SARS-CoV-2 infection in community settings was assessed as low to moderate strength favoring mask use, based on 2 RCTs (12, 13) and 8 observational studies (14–21). For this update, 2 new observational studies were consistent with prior evidence finding mask use associated with reduced risk for SARS-CoV-2 infection (Supplement Table 3). The adjusted odds ratio (OR) for mask use in public indoor settings versus no use was 0.51 (95% CI, 0.29 to 0.93) in 1 new study (7). The second, non–peer-reviewed study evaluated mask use for any interaction within a distance of less than 6 feet (excluding household members) (9). Wearing a mask for at least 1 day for such interactions within the preceding 10 days was associated with decreased risk for SARS-CoV-2 infection versus no mask use. The reduction in risk was similar in the pre-Delta (July 2020 to June 2021; adjusted OR, 0.60 [CI, 0.52 to 0.70]) and Delta-predominant (July 2021 to November 2021; adjusted OR, 0.65 [CI, 0.53 to 0.81]) eras but attenuated in the Omicron-predominant era (December 2021 to February 2022; adjusted OR, 0.86 [CI, 0.76 to 0.97]). Because the new studies were observational and had methodological limitations, the evidence for benefits of mask use versus no use for prevention of SARS-CoV-2 infection in the community remains low to moderate (Supplement Table 4).One of the new fair-quality studies (7) found surgical masks (adjusted OR, 0.34 [CI, 0.13 to 0.90]) and N95 or KN95 respirators (adjusted OR, 0.17 [CI, 0.05 to 0.64]) each associated with reduced risk for SARS-CoV-2 infection versus no mask use (Supplement Table 3). Cloth mask use was also associated with a reduced risk for infection compared with no use, but the estimate was imprecise (adjusted OR, 0.44 [CI, 0.17 to 1.17]). The study did not report risk estimates comparing mask types. On the basis of the adjusted estimates for masks versus no masks provided in the study, we calculated adjusted ORs for N95 and KN95 respirators versus surgical masks (adjusted OR, 0.50 [CI, 0.10 to 2.48]) and surgical versus cloth masks (adjusted OR, 0.77 [CI, 0.20 to 3.03]), which were imprecise. The correlation among the adjusted ORs was not reported; we assumed correlation equals 0, resulting in wider CIs than if correlation was present. The new fair-quality study provided insufficient evidence for N95 versus surgical mask (no prior studies) and did not change previous assessments (Supplement Table 4) of low strength of evidence for surgical masks versus no masks in community settings (based on 2 prior RCTs [12, 13] and 1 observational study [15]), low strength of evidence for no difference between surgical and cloth masks (based on 1 prior RCT [13] and 1 prior observational study [15]), and insufficient evidence for cloth masks versus no masks (based on 1 prior RCT [13] and 1 observational study [15]) and N95 respirators versus no masks (no prior studies).One other new study (8) evaluated the association between adherence to mask use among health care workers when outside of work and risk for SARS-CoV-2 infection, but the estimate was imprecise (for adherence all of the time versus most of the time, some of the time, or never: adjusted hazard ratio, 0.8 [CI, 0.5 to 1.6]). The strength of evidence for consistent or always mask use versus inconsistent mask use in the community is insufficient (no prior studies) (Supplement Table 4).Health Care SettingsTwo new cohort studies (10, 11) evaluated mask use and risk for SARS-CoV-2 infection in health care settings (Supplement Tables 2 and 4). One was a secondary publication (11) for a previously included study (22). In univariate analysis, it found N95 respirator use associated with increased risk for SARS-CoV-2 infection versus nonuse (OR, 7.8 [CI, 4.0 to 15.2]) (Supplement Table 3), but in multivariate analysis, the association between N95 respirator use was not statistically significant enough to be included in the multivariate model (criteria for selecting variables for model not reported); thus, the observed univariate association was likely related to confounding due to increased exposures or other factors in health care workers using N95 masks. The new study did not change the previous assessment of evidence on N95 versus no masks as insufficient (based on 3 prior studies [23–25]) (Supplement Table 4). One other new study (10) evaluated the association between consistency of mask use and risk for SARS-CoV-2 infection, but the estimate was very imprecise (for mask use at work all or nearly all of the time versus less than nearly all of the time (adjusted OR, 4.0 [CI, 0.7 to 19.5]) (Supplement Table 3). Therefore, the evidence on consistency of mask use remains insufficient (Supplement Table 4).Although this was planned as the final update, a large randomized trial of N95 versus surgical masks (26) has been completed, although results are not yet published. Because this trial could affect findings for this comparison, 1 additional update will be done after its publication.References1. Chou R, Dana T, Jungbauer R, et al. Masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. A living rapid review. Ann Intern Med. 2020;173:542-55. [PMID: 32579379] doi:10.7326/M20-3213 LinkGoogle Scholar2. Chou R, Dana T, Jungbauer R, et al. Update alert: masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings [Letter]. Ann Intern Med. 2020;173:W86. [PMID: 32687391] doi:10.7326/L20-0948 LinkGoogle Scholar3. Chou R, Dana T, Jungbauer R, et al. Update alert 2: masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings [Letter]. Ann Intern Med. 2020;173:132. [PMID: 32853032] doi:10.7326/L20-1067 LinkGoogle Scholar4. Chou R, Dana T, Jungbauer R, et al. Update alert 3: masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings [Letter]. Ann Intern Med. 2020;173:169. [PMID: 33105095] doi:10.7326/L20-1292 LinkGoogle Scholar5. Chou R, Dana T, Jungbauer R, et al. Update alert 4: masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings [Letter]. Ann Intern Med. 2021;174:W24. [PMID: 33370171] doi:10.7326/L20-1429 LinkGoogle Scholar6. Chou R, Dana T, Jungbauer R, et al. Update alert 5: masks for prevention of respiratory virus infections, including SARS-CoV-2, in health care and community settings. Ann Intern Med. 2021;174:W47. [PMID: 33683928] doi:10.7326/L21-0116 LinkGoogle Scholar7. Andrejko KL, Pry JM, Myers JF, et al; California COVID-19 Case-Control Study Team. Effectiveness of face mask or respirator use in indoor public settings for prevention of SARS-CoV-2 infection - California, February-December 2021. MMWR Morb Mortal Wkly Rep. 2022;71:212-16. [PMID: 35143470] doi:10.15585/mmwr.mm7106e1 CrossrefMedlineGoogle Scholar8. Doernberg SB, Holubar M, Jain V, et al; CHART Study Consortium. Incidence and prevalence of COVID-19 within a healthcare worker cohort during the first year of the SARS-CoV-2 pandemic. Clin Infect Dis. 2022. [PMID: 35279023] doi:10.1093/cid/ciac210 CrossrefMedlineGoogle Scholar9. Tjaden AH, Gibbs M, Runyon M, et al. Association between self-reported masking behavior and SARS-CoV-2 infection wanes from pre-Delta to Omicron-predominant periods—North Carolina COVID-19 Community Research Partnership. medRxiv. Preprint posted online 28 May 2022. doi:10.1101/2022.05.27.22275689 CrossrefGoogle Scholar10. Howard-Anderson JR, Adams C, Dube WC, et al. Occupational risk factors for severe acute respiratory coronavirus virus 2 (SARS-CoV-2) infection among healthcare personnel: a 6-month prospective analysis of the COVID-19 Prevention in Emory Healthcare Personnel (COPE) Study. Infect Control Hosp Epidemiol. 2022:1-8. [PMID: 35156597] doi:10.1017/ice.2021.518 CrossrefMedlineGoogle Scholar11. Piapan L, De Michieli P, Ronchese F, et al. COVID-19 outbreaks in hospital workers during the first COVID-19 wave. Occup Med (Lond). 2022;72:110-17. [PMID: 34919710] doi:10.1093/occmed/kqab161 CrossrefMedlineGoogle Scholar12. Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, et al. Effectiveness of adding a mask recommendation to other public health measures to prevent SARS-CoV-2 infection in Danish mask wearers. A randomized controlled trial. Ann Intern Med. 2021;174:335-43. [PMID: 33205991] doi:10.7326/M20-6817 LinkGoogle Scholar13. Abaluck J, Kwong LH, Styczynski A, et al. Impact of community masking on COVID-19: a cluster-randomized trial in Bangladesh. Science. 2022;375:eabi9069. [PMID: 34855513] doi:10.1126/science.abi9069 CrossrefMedlineGoogle Scholar14. Wang Y, Tian H, Zhang L, et al. Reduction of secondary transmission of SARS-CoV-2 in households by face mask use, disinfection and social distancing: a cohort study in Beijing, China. BMJ Glob Health. 2020;5. [PMID: 32467353] doi:10.1136/bmjgh-2020-002794 CrossrefMedlineGoogle Scholar15. Doung-Ngern P, Suphanchaimat R, Panjangampatthana A, et al. Case-control study of use of personal protective measures and risk for SARS-CoV 2 infection, Thailand. Emerg Infect Dis. 2020;26:2607-616. [PMID: 32931726] doi:10.3201/eid2611.203003 CrossrefMedlineGoogle Scholar16. van den Broek-Altenburg EM, Atherly AJ, Diehl SA, et al. Jobs, housing, and mask wearing: cross-sectional study of risk factors for COVID-19. JMIR Public Health Surveill. 2021;7:e24320. [PMID: 33315576] doi:10.2196/24320 CrossrefMedlineGoogle Scholar17. Gonçalves MR, Dos Reis RCP, Tólio RP, et al. Social distancing, mask use, and transmission of severe acute respiratory syndrome coronavirus 2, Brazil, April-June 2020. Emerg Infect Dis. 2021;27:2135-143. [PMID: 34087090] doi:10.3201/eid2708.204757 CrossrefMedlineGoogle Scholar18. Lio CF, Cheong HH, Lei CI, et al. Effectiveness of personal protective health behaviour against COVID-19. BMC Public Health. 2021;21:827. [PMID: 33926406] doi:10.1186/s12889-021-10680-5 CrossrefMedlineGoogle Scholar19. Rebmann T, Loux TM, Arnold LD, et al. SARS-CoV-2 transmission to masked and unmasked close contacts of university students with COVID-19 - St. Louis, Missouri, January-May 2021. MMWR Morb Mortal Wkly Rep. 2021;70:1245-48. [PMID: 34499631] doi:10.15585/mmwr.mm7036a3 CrossrefMedlineGoogle Scholar20. Sharif N, Alzahrani KJ, Ahmed SN, et al. Protective measures are associated with the reduction of transmission of COVID-19 in Bangladesh: a nationwide cross-sectional study. PLoS One. 2021;16:e0260287. [PMID: 34807962] doi:10.1371/journal.pone.0260287 CrossrefMedlineGoogle Scholar21. Sugimura M, Chimed-Ochir O, Yumiya Y, et al. The association between wearing a mask and COVID-19. Int J Environ Res Public Health. 2021;18. [PMID: 34501719] doi:10.3390/ijerph18179131 CrossrefMedlineGoogle Scholar22. Piapan L, De Michieli P, Ronchese F, et al. COVID-19 outbreak in healthcare workers in hospitals in Trieste, North-east Italy. J Hosp Infect. 2020;106:626-8. [PMID: 32805309] doi:10.1016/j.jhin.2020.08.012 CrossrefMedlineGoogle Scholar23. Sims MD, Maine GN, Childers KL, et al. Coronavirus disease 2019 (COVID-19) seropositivity and asymptomatic rates in healthcare workers are associated with job function and masking. Clin Infect Dis. 2021;73:S154-62. [PMID: 33150375] doi:10.1093/cid/ciaa1684 CrossrefMedlineGoogle Scholar24. Wang X, Pan Z, Cheng Z. Association between 2019-nCoV transmission and N95 respirator use [Letter]. J Hosp Infect. 2020;105:104-5. [PMID: 32142885] doi:10.1016/j.jhin.2020.02.021 CrossrefMedlineGoogle Scholar25. Venugopal U, Jilani N, Rabah S, et al. SARS-CoV-2 seroprevalence among health care workers in a New York City hospital: a cross-sectional analysis during the COVID-19 pandemic. Int J Infect Dis. 2021;102:63-9. [PMID: 33075539] doi:10.1016/j.ijid.2020.10.036 CrossrefMedlineGoogle Scholar26. Medical Masks vs N95 Respirators for COVID-19 [clinical trial]. Accessed at www.clinicaltrials.gov/ct2/show/NCT04296643 on 29 June 2022. Google Scholar Comments0 CommentsSign In to Submit A Comment Jesper M Kivelä, specialising physician DMedScHelsinki, Finland5 August 2022 A paucity of high-quality mask studies is unfortunate Chou and coworkers published their eighth update for prevention of respiratory virus infections with masks (1). There seems to be inconsistency considering strength of evidence for SARS-CoV-2 in community setting since evidence was deemed as low/moderate in text but insufficient/low in Supplement Table 4. The authors pointed out that evidence for cloth mask was imprecise based on a study by Andrejko and colleagues (2). One can calculate upper to lower confidence limit ratio (3), which is 7 for both cloth (1.17/0.17) and surgical (0.90/0.13) mask, but 13 (0.64/0.05) for N95/KN95 respirator. Thus, estimate for cloth mask is equally or more precise compared to the other two estimates even though statistically not significant. Additionally, comparison of mask types seems to be attached to wrong study (namely to reference 9) in the Supplement Table 4. So far, two randomized controlled mask trials for prevention of SARS-CoV-2 infection have been published (4,5). Posterior median for relative risk was 0.91 (95% credible interval 0.63 to 1.33, 73% probability of some benefit) based on a Bayesian random-effects meta-analysis of these two trials (6). A paucity of high-quality mask studies is unfortunate despite the third year of pandemic. References 1. Chou R, Dana T, Jungbauer R. Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings. Ann Intern Med 2022 Jul 26. doi: 10.7326/L22-0272. 2. Andrejko KL, Pry JM, Myers JF, et al. Effectiveness of Face Mask or Respirator Use in Indoor Public Settings for Prevention of SARS-CoV-2 Infection - California, February-December 2021. MMWR Morb Mortal Wkly Rep 2022;71:212-216. 3. Poole C. Low P-values or narrow confidence intervals: which are more durable? Epidemiology 2001;12:291-4. 4. Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, et al. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers: A Randomized Controlled Trial. Ann Intern Med 2021;174:335-343. 5. Abaluck J, Kwong LH, Styczynski A, et al. Impact of community masking on COVID-19: A cluster-randomized trial in Bangladesh. Science 2022;375(6577):eabi9069. 6. Kivelä JM. Re: Public health measures for covid-19. https://www.bmj.com/content/375/bmj.n2729/rr-3 (accessed 1 August 2022) Roger Chou, MD, Tracy Dana, MLS, Rebecca Jungbauer, DrPHPacific Northwest Evidence-based Practice Center, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, Oregon26 September 2022 Author Response to Kivelä Kivelä noted errors in Supplement Tables 3 and 4 to Update Alert 8 for our living review on masks and respiratory virus infections, including SARS-CoV-2 (1). In Supplement Table 3, the calculated odds ratios for comparisons of masks types (N95/KN95 versus surgical mask and surgical mask versus cloth mask in household contacts and community settings) were placed with the study by Tjaden et al (2), when they should have been placed with the study by Andrejko et al (3). In Supplemental Table 4, for mask (type not specified) versus no mask in household contacts and other community settings, the symbols for strength of evidence should have indicated low or moderate strength of evidence (rather than low or insufficient). We regret these errors and have issued a correction. The results and strength of evidence were described in the main text of Update Alert 8 and not affected by the corrections. Kivelä also reported a Bayesian random-effects meta-analysis of two randomized controlled trials (4, 5) of masks in community settings. We did not conduct meta-analysis because there were only two trials, with differences in the intervention evaluated (a recommendation to wear masks versus a mask promotion intervention), settings (Denmark versus Bangladesh), and outcomes (SARS-CoV-2 infection by antibody testing, polymerase chain reaction, or hospital diagnosis versus symptomatic SARS-CoV-2 seroprevalence). References Chou R, Dana T, Jungbauer R. Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings. Ann Intern Med. 2022 Jul 26. doi: 10.7326/L22-0272. Epub ahead of print. PMID: 35878407. Tjaden AH, Gibbs M, Runyon M, et al.Association between self-reported masking behavior and SARS-CoV-2 infection wanes from pre-Delta to Omicron-predominant periods—North Carolina COVID-19 Community Research Partnership. medRxiv. Preprint posted online 28 May 2022. doi:1101/2022.05.27.22275689. Andrejko KL, Pry JM, Myers JF, et al; California COVID-19 Case-Control Study Team. Effectiveness of face mask or respirator use in indoor public settings for prevention of SARS-CoV-2 infection - California, February-December 2021.MMWR Morb Mortal Wkly Rep. 2022;71:212-16. doi:15585/mmwr.mm7106e1. PMID: 35143470 Bundgaard H, Bundgaard JS, Raaschou-Pedersen DET, et al. Effectiveness of Adding a Mask Recommendation to Other Public Health Measures to Prevent SARS-CoV-2 Infection in Danish Mask Wearers : A Randomized Controlled Trial. Ann Intern Med. 2021 Mar;174(3):335-343. doi: 10.7326/M20-6817. PMID: 33205991. Abaluck J, Kwong LH, Styczynski A, et al. Impact of community masking on COVID-19: A cluster-randomized trial in Bangladesh. Science. 2022 Jan 14;375(6577):eabi9069. doi: 10.1126/science.abi9069. PMID: 34855513. Author, Article, and Disclosure InformationAuthors: Roger Chou, MD; Tracy Dana, MLS; Rebecca Jungbauer, DrPHAffiliations: Pacific Northwest Evidence-based Practice Center, Department of Medical Informatics and Clinical Epidemiology, Oregon Health & Science University, Portland, OregonDisclaimer: The authors of this manuscript are responsible for its content. Statements in the manuscript do not necessarily represent the official views of or imply endorsement by the Agency for Healthcare Research and Quality or U.S. Department of Health and Human Services.Disclosures: Disclosures can be viewed at www.acponline.org/authors/icmje/ConflictOfInterestForms.do?msNum=L22-0272.Corresponding Author: Roger Chou, MD, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Mail Code BICC, Portland, OR 97239; e-mail, chour@ohsu.edu.This article was published at Annals.org on 26 July 2022. PreviousarticleNextarticle Advertisement FiguresReferencesRelatedDetailsSee AlsoUpdate Alert: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , Chandler Weeks , and Marian S. McDonagh Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , Chandler Weeks , and Marian S. McDonagh Update Alert 2: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , Chandler Weeks , and Marian S. McDonagh Update Alert 3: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , and Chandler Weeks Update Alert 4: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , and Chandler Weeks Update Alert 5: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer , and Chandler Weeks Update Alert 6: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , and Rebecca Jungbauer Update Alert 7: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community Settings Roger Chou , Tracy Dana , Rebecca Jungbauer Correction: Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community SettingsMajor Update: Masks for Prevention of SARS-CoV-2 in Health Care and Community Settings—Final Update of a Living, Rapid Review Roger Chou , and Tracy Dana Metrics Cited byMajor Update: Masks for Prevention of SARS-CoV-2 in Health Care and Community Settings—Final Update of a Living, Rapid ReviewRoger Chou, MD, and Tracy Dana, MLSComparative Effectiveness of Mask Type in Preventing SARS-CoV-2 in Health Care Workers: Uncertainty PersistsRoger Chou, MDCorrection: Update Alert 8: Masks for Prevention of Respiratory Virus Infections, Including SARS-CoV-2, in Health Care and Community SettingsA multinational Delphi consensus to end the COVID-19 public health threat September 2022Volume 175, Issue 9Page: W108-W109 ePublished: 26 July 2022 Issue Published: September 2022 Copyright & PermissionsCopyright © 2022 by American College of Physicians. 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